A last word from me as well, then.

I agree that a world in which immortality would be possible would look very different from today's, but that's because the development of immortality would require technological advances (maybe nanotechnology) that would change the world by themselves even if they didn't lead to immortality. Immortality by itself wouldn't make the world look that different, though - funeral homes would go out of business, and maybe hospitals as well, but other than that, it wouldn't make a huge difference.

I think novelty is highly overrated as a source of value. Certainly, it's nice to play a good new game or something like that, but as far as possible sources of value, it's quite low on the list. Regarding having children, the parent-child bond is part of human nature, so I don't think it'll ever become trivial. As for hedonism, I don't expect it to ever lose its appeal, especially as new fun things are created.

It's an opportunity cost argument, right? Okay. Except you cease to exist in this particular case.

Yes, it is an opportunity cost, and the fact that you wouldn't exist is the problem, because it means that instead of getting something positive, you'd be getting nothing.